The invention relates to adaptors to minimize the number of double taper collet chucks required in an automated machining operation. Commercially available collet chucks are available to accept various collet ranges, such as 1/16" to 1/4", 1/8" to 5/8", 3/16" to 1/2", 5/8" to 3/4", 5/8" to 1" and 3/4" to 11/2". Hence, in multiple step machining operations changeover of different chuck sizes may be required when changing drill sizes, resulting in down time of the machine.